A technical problem to be solved is the location of a vertical takeoff or landing craft for which a very high precision of location is sought, according to an economical solution.
This need may relate to the guidance of rotary-wing aircraft, piloted or not, but more particularly to novel systems intended to recover the first stage of rocket launchers.
In this particular case the descent speed is high, thus rendering guidance towards the landing zone very tricky.
Moreover, these systems require very high operating safety, given the cost of the craft that one wishes to recover and the risks incurred, in particular the risks of crashing in an inhabited area.
There exist numerous systems for aiding landing, in particular based on radar technology. Most of these systems are suited to the landing of aircraft carrying out an approach to the touchdown point along a low descent slope, typically 3° and with a relatively low descent speed. The P.A.R. (Precision Approach Radar) system may in particular be cited in this regard.
All these systems are intended to detect long-range targets, typically several tens of kilometres away, thus requiring antennas of large dimensions and high emission power.
They are expensive, unwieldy to implement or are poorly suited to the guidance of craft carrying out a vertical or near-vertical descent slope, in particular when the descent speed is high.